How do you reach an accurate differential diagnosis of diarrhoea in dogs?
Diarrhoea and vomiting are very persistent clinical signs that affect a lot of dogs and their treatment tends to be frustrating for the patient, owner and veterinary surgeon because it is often hard to identify the underlying aetiology.
Early diagnostic problems: the owner’s doubts and fears
Once acute diarrhoea has been excluded from the diagnosis following the standard treatment of 2–4 weeks, it is worth spending the time and money to obtain a specific diagnosis to guide the management of the problem. However, first of all, the diagnostic approach must be agreed with the owner, taking into account each owners’ specific situation and the animal’s character and disorder.
It is a good idea to give the owner a clear explanation of the possible options and the procedures required in each case, assess the diagnostic facilities available and estimate the total cost (1). The owner needs to understand that a more accurate diagnosis will improve the chances of successfully resolving the clinical picture, and that this requires patience. As the vet, you should also clarify that the diagnosis and treatment will probably involve a change in the dog’s dietary habits.
What criteria should I apply in the differential diagnosis of each specific case? - Algorithms -
The differential diagnosis is based on the logical application of tests, while always bearing in mind the pathophysiology of diarrhoea.
Most gastrointestinal diseases have very similar, nonspecific clinical signs including weight loss, poor appetite, diarrhoea, vomiting, abdominal tenderness, and so on, which makes it even harder to determine the particular disorder in each case. This is why differential diagnostic algorithms are used in diarrhoea, since they help identify specific disorders, assess the severity, rule out certain diseases, establish a diagnostic plan, and finally implement a treatment tailored to each case.
The following image presents a detailed differential diagnostic algorithm for chronic diarrhoea.
Step-by-step diagnosis
- Clinical history
An accurate anamnesis and complete clinical examination should, at the very least, include the amount and type of food consumed, possible contact with other diarrhoetic dogs, an abdominal palpation and a rectal exam.
- General tests
As shown by the attached algorithm, general tests, such as blood tests, urinalysis and ultrasound, are useful for ruling out specific causes.
- Drug therapies and dietary treatments used in the diagnosis
Chronic gastroenteritis can be classified into four groups depending on treatment response: food sensitivities (respond to dietary changes), antibiotic-responsive diarrhoea (ARD), steroid-responsive diarrhoea and idiopathic inflammatory bowel disease (IBD) which only responds to immunosuppressants.
Biopsy or no biopsy?
The method traditionally used to guide diagnosis involves collecting biopsy samples from the duodenal and intestinal mucosae using endoscopy under general anaesthesia for subsequent histological analysis. However, instead of a precise diagnosis, this technique usually only provides a description of the histopathological changes, which does not affect the treatment as the options remain similar.
The therapeutic agents used to treat chronic enteropathies may have unacceptable side effects, they could be prohibitively expensive, lose their efficacy and, in many cases, they may be unnecessary.
An excellent option is the dietary treatment of diarrhoea
In many cases, diet is a good ally in the differential diagnosis of diarrhoea and, furthermore, proves to be a very effective, economical and safe treatment for patients. Additionally, hypoallergenic diets and diets for treating gastrointestinal disorders that are currently being developed have excellent palatability and dogs eat them with enthusiasm, which in turn facilitates weight regain.
Several studies have reported that 70–90% of cases of chronic enteropathy are due to a food sensitivity (2). This opens the door to a dietary treatment that will result in greater diagnostic agility for the vet and fewer invasive procedures for the dog.
Bibliography:
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C.F. Burrows. Consideraciones diagnósticas sobre la diarrea crónica en el perro y en el gato. AVEPA magazine 1988; 8(2): 61-69. Available at: http://ddd.uab.cat/pub/clivetpeqani/11307064v8n2/11307064v8n2p61.pdf
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A. Lynch. A study of dietary modulation in canine inflammatory enteropathies. PhD thesis, University of Bristol, 2013. Available at: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.573497
